Yes a little more it also depends on whether or not they have the reamer and stock your typical gunsmith charging your typical prices may not spend the time to do it properly a $250 chamber job is not what I would call a quality job on any caliber or cartridge
Proper way to do it would be to check and Face action thread and hand lap index vertically chamber and polish install brake and index brake 750.00 if I was still doing gunsmith work for the public that price also included breaking in Barrel and developing loads
Proper setup is more important then how precise your lathe is if you have the most precise lathe on the face of the Earth but you have run out in your setup the quality of the lathe won't make a difference. Even the cheapest equipment made in China set up properly are more than adequate for a quality finished job
Yes, definitely costs more. Everything is heavier and takes extra time. Everything about the job takes longer as their is more setup time and more metal to remove. I charge $600 for anything over a 338.